This application claims priority to German Patent Application No. 199 12 470.1 filed on Mar. 19, 1999 and International Application No. PCT/DE00/00726 filed on Mar. 8, 2000.
The invention concerns a process for the production of composite parts, in which a magnet body made of an alloy rich in rare earths is bonded with a soft-magnetic support body along a boundary surface.
The invention further concerns a composite part with a magnet body based on an alloy rich in rare earths and a soft-magnetic support body.
These types of composite parts are, for example, used in electric motors as rotors or stators. For this purpose, the soft-magnetic support body serves as the magnetic return body for the magnet body. To produce these composite parts, a magnet body is first compacted from a powder based on an alloy rich in rare earths and then sintered. Due to the large reduction in volume during the sintering, this magnet body displays poor dimensional accuracy, so that after sintering it must be ground to measure. After grinding, the magnet body is glued to the soft-magnetic support body and assembled into rotors or stators of an electric motor.
A disadvantage of the known composite part and the known process is that an appropriate allowance must be reserved for the grinding of the magnet body. During the grinding away of this allowance, there is a large amount of waste. As a consequence, expensive material is thus wasted. In addition, the grinding waste produces disposal problems. Furthermore, the magnets must be presorted due to their warping, in order to keep the grinding costs within limits. Therefore, the grinding costs determine the magnet costs to a large degree, particularly when several surfaces have to be ground.
Proceeding from this prior art, the invention has as its object the creation of a dimensionally stable composite part of high strength made of a magnet body and a soft-magnetic support body and the indication of a simple and economical process for its production.
This object is achieved according to the invention in that a molten phase implemented along a boundary surface extends from the magnet body into the support body.
Furthermore, this object is achieved according to the invention by a process with the following process steps:
a) the support body and the magnet body are molded from powder,
b) a molten phase is formed in the region of the boundary surface by a heat treatment which penetrates into the support body during the heat treatment
The production of the support body using powder metallurgy leads to the support body having numerous pores and channels along the boundary surface, into which the molten phase present in the region of the boundary surface during the heat treatment can enter. The magnet body is effectively anchored in the support body after cooling by the molten phase which has penetrated into the magnet body. The anchoring of the magnet body in the support body is so strong in this case that the bond of the support body with the magnet body is maintained during the cooling after the joint sintering in spite of differing thermal expansion coefficients. Because there are numerous possibilities for designing the geometry of the support body and a high degree of dimensional accuracy of the composite part according to the invention is provided, the composite parts produced according to the invention can be assembled into complex electromechanical components through connectors or clamps directly after the heat treatment, without further grinding procedures.
Further embodiments and advantageous implementations of the invention are indicated in the dependent claims.